Windchill PDMLink のイベント マネージャで「オブジェクトが不適切に初期化されました (つまり、null でした)」というエラーが発生し、CAD ドキュメントのチェックアウトを元に戻すことができません。

• ユーザーと管理者は特定のCADドキュメントのチェックアウトを元に戻すことができません
• ユーザーワークスペースからオブジェクトを削除したりチェックアウトを元に戻すことはできません
• イベントマネージャに次のエラーがあります

The object was improperly initialized (i.e., it was null)
INFO  : com.ptc.windchill.uwgm.proesrv.StandardRequestDispatcher wcadmin - StandardRequestDispatcher.dispatchRequest ::  >   UWGM request: UnlockIterations_i
INFO  : com.ptc.windchill.uwgm.proesrv.action.UnlockIterationAction wcadmin - UnlockIterationAction.executeAction :: Begin Unlock Iterations ...
ERROR : com.ptc.windchill.uwgm.proesrv.action.UnlockIterationAction wcadmin - UnlockIterationAction.executeAction ::
(wt.vc.wip.wipResource/0) wt.vc.wip.WorkInProgressException: The object was improperly initialized (i.e., it was null).
at wt.vc.wip.StandardWorkInProgressService.validateAccessForUndoCheckout(StandardWorkInProgressService.java:2897)
at wt.vc.wip.StandardWorkInProgressService.undoCheckouts(StandardWorkInProgressService.java:1102)
at sun.reflect.GeneratedMethodAccessor4127.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at wt.services.ServiceFactory$ServerInvocationHandler.invoke(ServiceFactory.java:314)
at $Proxy33.undoCheckouts(Unknown Source)
at com.ptc.windchill.uwgm.proesrv.action.UnlockIterationAction.executeAction(UnlockIterationAction.java:70)
at com.ptc.windchill.uwgm.proesrv.request.UnlockIterationsRequest.executeRequest(UnlockIterationsRequest.java:91)
at com.ptc.windchill.uwgm.proesrv.StandardRequestDispatcher.dispatchRequest(StandardRequestDispatcher.java:1001)
at com.ptc.windchill.uwgm.proesrv.StandardRequestDispatcher.scanRequests(StandardRequestDispatcher.java:862)
at com.ptc.windchill.uwgm.proesrv.UwgmTransactionExecuterImpl.execute(UwgmTransactionExecuterImpl.java:94)
at com.ptc.windchill.uwgm.proesrv.UwgmTransactionExecuterImpl.executeTransaction(UwgmTransactionExecuterImpl.java:56)
at com.ptc.windchill.uwgm.proesrv.ProeService.executeTransaction(ProeService.java:102)
at com.ptc.windchill.uwgm.proesrv.ProeService.execute(ProeService.java:80)
at com.ptc.windchill.uwgm.cadx.request.UwgmRequestProcessor.process(UwgmRequestProcessor.java:45)
Stacktrace from 10.0 M020